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https://issues.apache.org/jira/browse/LOG4J2-585?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13967953#comment-13967953
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Bruce Brouwer commented on LOG4J2-585:
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* I like the new fluent API. 
* Do you think it will be confusing that we have one method called simply set, 
add or remove, while the getter is called getParents()? I'm thinking 
particularly about the set vs. getParents. 
* You synchronized add and remove, but not set. I know it isn't absolutely 
necessary, but might it cause confusing behavior if some race condition 
occurred from client code calling add and set concurrently? I doubt 
synchronizing set is going to cause serious performance problems. 
* Commentary: Alternatively, in getParents, you could simply return 
{{Arrays.copyOf(this.parents, this.parents.length);}} instead of creating a 
temporary array and calling {{System.arraycopy(...)}}. But what you wrote works 
perfectly fine. 
* It looks like you implemented what I asked regarding 
{{this.isInstanceOf(parent)}} by implementing that {{contains}} method. I like 
it. Thanks. 
* I see you deprecated the getMarker methods that specify a parent. Thanks. Is 
it the plan to remove deprecated methods before 2.0 GA? 

> Markers not as powerful as slf4j
> --------------------------------
>
>                 Key: LOG4J2-585
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-585
>             Project: Log4j 2
>          Issue Type: Improvement
>          Components: API
>    Affects Versions: 2.0-rc1
>            Reporter: Bruce Brouwer
>         Attachments: ConceptMarkerBenchmark.java, 
> CurrentMarkerBenchmark.java, log4j2-585-concept.patch
>
>
> Log4J's markers are not as flexible as markers in SLF4J. 
> First, SLF4J's markers are mutable. By allowing markers to be mutable, I can 
> change the relationship of markers to each other based upon runtime or 
> business conditions. 
> Second, and more importantly I think, is that essentially SLF4J markers have 
> this parent/child relationship, much like Log4J, except that in SLF4J, I can 
> essentially have a marker with multiple parents. For example, I might want 
> this structure:
> * Animal
> ** Bird
> *** Duck
> ** Mammal
> *** Bear
> *** Dolphin
> * Travels by
> ** Water
> *** Duck
> *** Dolphin
> ** Land
> *** Duck
> *** Bear
> ** Air
> *** Duck
> Of course, this is a contrived example, but I wanted to describe the 
> relationships. Now, if I wanted to filter based on markers that travel by 
> Water for some appenders, and another appender wants to filter by Mammals, I 
> can't simply use the single marker of Dolphin. 
> Either we need to reverse the marker relationship so that it contains its 
> children, much like SLF4J, or we allow markers to have multiple parents, 
> which I prefer because it could make it more succinct to define:
> {code}
> private static final Marker BY_LAND = MarkerManager.getMarker("BY_LAND");
> private static final Marker BY_WATER = MarkerManager.getMarker("BY_WATER");
> private static final Marker DUCK = MarkerManager.getMarker("DUCK", BY_LAND, 
> BY_WATER);
> {code}
> As for the Marker API, we would either need to change getParent to 
> getParents, or get rid of the getParent method from the API and just rely on 
> the isInstanceOf method to handle checking multiple parents by looking at 
> private member variables (my preference)



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